A range of bandages are known which are adhesive on the side facing the skin or the wound, especially adhesive plasters, and -- most important in the present context -- in the form of skin barriers having a continuous phase of a skin-friendly, adhesive material preferably comprising an elastomer such as a styrene-olefine-styrene block copolymer, a natural rubber or silicone rubber. The adhesive material may be polymers and copolymers of dicyclopentadiene or pinene, or it may be polyisobutylene or similar substances. According to known technique one or more hydrocolloids may be present as a separate disperse phase. Examples of patent specifications describing this technique are U.S. Pat. No. 3,339,546, U.S. Pat. No. 4,231,369 and U.S. Pat. No. 4,367,732. At least the skin barriers known from the two latter specifications are liquid-absorbing.
In the skin and wound treatment it is known to incorporate biologically active substances, for instance antibiotics and antiseptics, in the continuous phase of such adhesive bandages, cf. e.g. EP patent specification No. 55,023 which recommends the incorporation of antiseptics in order to protect the bandage itself; U.S. Pat. No. 4,307,717; DK patent specification No. 109,225, cf. especially Examples 7-9; U.S. Pat. Nos. 4,231,369 and 4,367,732 referred to above; and the U.S. Pat. Nos. 370,893 of Apr. 22, 1982 and 507,657 of Jun. 27, 1983. European patent publication No. 272,149 suggests incorporating a biologically active substance in a separate phase which is dispersed in the continuous phase, thereby obtaining a liquid-dependent release of the active substance, whereas the active substance is released substantially independently of liquid from the bandages in which it is present in the continuous phase.
From various patent specifications, i.a. EP publication No. 63,604, PCT publication No. W082/00099 and U.S. Pat. No. 3,769,071 it is known to cut sheets of bandages, having incorporated therein a biologically active material, into corpuscles which are placed on the patient on the site of treatment.
From U.S. Pat. No. 4,597,960 an astrigent hemostatic preparation is known which is provided with a granulated hemostatic (an inorganic aluminium or ferric salt) encapsulated in a cellulose-based, biocompatible polymer which is soluble in body fluids. The granulated hemostatic itself may be particles which are attached to an adhesive layer on an absorbing pad, for instance made from gauze or a foam material, and these elements together may form corpuscles which are attached to the adhesive surface of a conventional bandage provided with an adhesive layer. The side of the granulated hemostatic facing the skin may optionally be covered with a further layer of an adhesive which on the side facing the skin is provided with a further absorbing pad of the same kind as that mentioned above. The hemostatic effect will occur when the capsule-forming polymer is dissolved by the body fluids whereby no substantial delay nor protracted effect of the aluminium or ferric salts will occur.
EP patent specification No. 170,010 describes a self-adhesive plaster comprising approximately spherical cap-shaped segments containing one or more biologically active substances arranged on a carrier for transdermal administration and, in order to exert an adhesive effect on the biologically active substance, also comprising approximately spherical cap-shaped adhesive segments spatially separated from the active substance segments and comprising adhesive systems which can be processed as a dispersion, plastisol or organosol. The micro-structure of the biologically active segments has not been explained, but according to the Example of the specification they consist of a thickened organic solution of the active substance. The plaster is manufactured by applying the respective segments by means of a screen printer. The active segments are cut from a sheet of segment material by means of a sieve cylinder. The way of manufacture makes it difficult to provide the plaster with active segments of different composition, including concentration.
GB No. 2,184,019 A describes a transdermal or dermal patch in which an active substance has been embedded in a number of compartments which are enclosed between a backing layer, which is impermeable to the active substance, and a membranous layer, through which it is able to penetrate. The active substance is present in the compartments as a dispersion or solution in a more or less low-viscosity fluid or an ointment-like substance. The specification emphasizes that the carrier fluid may be more liquid than that used in known plasters comprising only one compartment instead of a number of compartments. It is, however, said that the compartments may be 30 cm.sup.2, but preferably not more than 20 or 13.3 cm.sup.2. Compartments that large will not allow a very precise control of the delivery rate of the active substance, for instance to vary it within a very few cm.
It is the object of the invention to provide a dressing material of the kind stated in the opening paragraph, which differs from the known technique by being suitable for a very varied, individual wound treatment which can be adapted very precisely to the site of treatment and which due to the structure thereof releases the biologically active substance or substances slowly by virtue of penetration of wound exudate through the matrix.